Er3+-doped and Er3+-Yb3+ co-doped yttrium aluminum borate (YAB) single crystals have been grown by the top-seeded solution growth method using a new flux system, namely NaF-MoO3-B2O3. The Er3+ concentrations were 1.3 mol% for both single doped and co-doped crystals and the Yb3+ concentration in the Er3+-Yb3+ co-doped crystal was 20.0 mol% in the raw materials. The distribution coefficients of Er3+ single doped and Er3+-Yb3+ co-doped crystals were measured. The polarized absorption and fluorescence spectra of Er3+-Yb3+ co-doped crystal were recorded and compared with those of Er3+ single doped crystal. The results demonstrate that Er3+-Yb3+ co-doped YAB crystal is a potential candidate for 1.55 mum laser materials. (C) 2004 Elsevier B.V. All rights reserved.